Distribution of omega-6 and omega-3 polyunsaturated fatty acids in the whole rat body and 25 compartments

The steady state compositions of omega-6 and omega-3 polyunsaturated fatty acids (PUFA) throughout the various viscera and tissues within the whole body of rats have not previously been described in a comprehensive manner. Dams consumed diets containing 10 wt% fat (15% linoleate and 3% α-linolenate). Male offspring (n=9) at 7-week of age were euthanized and dissected into 25 compartments. Total lipid fatty acids for each compartment were quantified by GC/FID and summed for the rat whole body; total n−6 PUFA was 12 wt% and total n−3 PUFA was 2.1% of total fatty acids. 18:2n−6 accounted for 84% of the total n−6 PUFA, 20:4n−6 was 12%, 18:3n−3 was 59% of the total n−3 PUFA, 20:5n−3 was 2.1%, and 22:6n−3 was 32%. The white adipose tissue contained the greatest amounts of 18:2n−6 (1.5 g) and 18:3n−3 (0.2 g). 20:4n−6 was highest in muscle (60 mg) and liver (57 mg), while 22:6n−3 was greatest in muscle (46 mg), followed by liver (27 mg) and carcass (20 mg). In terms of fatty acid composition expressed as a percentage, 18:2n−6 was the highest in the heart (13 wt%), while 18:3n−3 was about 1.3 wt% for skin, white adipose tissue and fur. 20:4n−6 was highest (21-25 wt%) in the circulation, kidney, and spleen, while 22:6n−3 was highest in the brain (12 wt%), followed by the heart (7.9 wt%), liver (5.9 wt%), and spinal cord (5.1 wt%). Selectivity was greatest when comparing 22:6n−3 in brain (12%) to white adipose (0.08%) (68-fold) and 22:5n−6 in testes (15.6%) compared to white adipose (0.02%), 780-fold.